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ABOUT LEMS

Lambert-Eaton myasthenic syndrome (LEMS) is a disorder of the neuromuscular junction8

Neuromuscular junction (NMJ) disorders may be the result of exposure to certain toxins, immune-mediated diseases, or genetic disorders.8

Chart showing neuromuscular junction disorders Chart showing neuromuscular junction disorders
While all neuromuscular junction disorders are uncommon, the immune-mediated diseases—LEMS and MG—are the ones most often encountered in the EMG lab.8

KEY FACTS ABOUT LEMS

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    SYMPTOMS

    LEMS is a rare, immune-mediated neuromuscular disorder characterized by a clinical triad of signs and symptoms: proximal muscle weakness, autonomic symptoms, and hyporeflexia or areflexia.12 See more on the LEMS Symptoms Map.

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    BURDEN

    LEMS results in diminished physical functionality as well as impairments in activities of daily living (ADL) and patients’ quality of life.5

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    PREVALENCE

    LEMS is estimated to affect up to 3,000 individuals in the United States11—up to 58% of whom are previously diagnosed with another condition12

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    COMORBIDITY

    Historically, more than half of LEMS cases are associated with an underlying cancer, usually small cell lung cancer (SCLC).13 Studies suggest that LEMS patients with SCLC display a more rapidly progressing course of disease vs those with LEMS not associated with SCLC.14,15 Because LEMS symptoms often precede tumor detection by months or even years16, LEMS patients’ lives may be saved by earlier diagnosis and treatment of the cancer.

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    PATHOPHYSIOLOGY

    LEMS is caused by autoantibodies to presynaptic voltage-gated calcium channels (VGCCs) that reduce the release of acetylcholine into the NMJ, inhibiting neuromuscular transmission.17-19

LEMS mechanism of disease

DISEASE BURDEN

Progression of LEMS symptoms contributes to worsening disease burden5

IN A 2012 SURVEY OF PATIENTS LIVING WITH LEMS5:

75% reported partial or total restriction of activities of daily living5, such as rising from a chair or climbing stairs6

50% reported severe leg weakness; other frequently reported symptoms included dry mouth and difficulty focusing eyesight5

Based on EQ-5D scores, the health-related quality of life for LEMS patients is comparable to the most severe forms of multiple sclerosis5

In a 2001 study, ~25% of LEMS patients required a wheelchair all the time or for mobilization outside the home20

A CHALLENGING DIAGNOSIS

LEMS patients often experience a long diagnostic journey5

The mean time to a LEMS diagnosis is 4.4 years The mean time to a LEMS diagnosis is 4.4 years

REASONS FOR THE DELAYS IN DIAGNOSIS:

  • Nonspecific and fluctuating symptoms12
  • Slow progression of disease12
  • Similar clinical presentation to other conditions12,21
Despite the significant burden it places on patients and their families, LEMS is often underrecognized5

THE DIAGNOSTIC CONUNDRUM

Studies reveal that more than half of patients with LEMS received a different diagnosis first12,21

THE DIAGNOSTIC CONUNDRUM THE DIAGNOSTIC CONUNDRUM

In a cohort of 241 adult patients with LEMS, 58% were diagnosed with another disorder at least once before receiving the correct diagnosis.12

Clinical presentation of LEMS resembles other common diagnoses12,21

The symptoms of LEMS are often mistaken for common diseases and disorders, such as myasthenia gravis (MG), multiple sclerosis (MS), Guillain-Barré syndrome, amyotrophic lateral sclerosis (ALS), and depression.12,21

INITIAL DIAGNOSES PRIOR TO CONFIRMATION OF LEMS (n=140)12

Prevalence of misdiagnoses among patients with LEMS12

Pie chart showing initial LEMS diagnoses
  • MG
  • Muscular abnormalities
  • Peripheral nerve abnormalities
  • Intracranial/spinal cord abnormalities
  • Depression
  • Other
  • MG
  • Intracranial/spinal cord abnormalities
  • Muscular abnormalities
  • Depression
  • Peripheral nerve abnormalities
  • Other
More than 1/3 of LEMS patients were previously diagnosed as having MG12
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Indication and Important Safety Information

indications and usage:

FIRDAPSE is a potassium channel blocker indicated for the treatment of Lambert-Eaton myasthenic syndrome (LEMS) in adults and pediatric patients 6 years of age and older.

CONTRAINDICATIONS

FIRDAPSE is contraindicated in patients with:

  • A history of seizures
  • Hypersensitivity to amifampridine phosphate or another aminopyridine

WARNINGS AND PRECAUTIONS

Seizures: FIRDAPSE can cause seizures. Consider discontinuation or dose-reduction of FIRDAPSE in patients who have a seizure while on treatment.

Hypersensitivity: If a hypersensitivity reaction such as anaphylaxis occurs, FIRDAPSE should be discontinued and appropriate therapy initiated.

ADVERSE REACTIONS

The most common (> 10%) adverse reactions are: paresthesia, upper respiratory tract infection, abdominal pain, nausea, diarrhea, headache, elevated liver enzymes, back pain, hypertension, and muscle spasms.

Please see full Prescribing Information for additional Important Safety Information.

To report SUSPECTED ADVERSE REACTIONS, contact Catalyst Pharmaceuticals at 1-844-347-3277 (1-844-FIRDAPSE) or FDA at 1-800-FDA-1088 or www.fda.gov/medwatch.

References:
  1. Yoon CH, Owusu-Guha J, Smith A, Buschur P. Amifampridine for the management of Lambert-Eaton myasthenic syndrome: a new take on an old drug. Ann Pharmacother. 2020;54(1):56-63.
  2. Full Prescribing Information for FIRDAPSE (amifampridine). Catalyst Pharma; 2022.
  3. Oh SJ, Scherbakova N, Kostera-Pruszczyk A, et al; LEMS Study Group. Amifampridine phosphate (FIRDAPSE®) is effective and safe in a phase 3 clinical trial in LEMS. Muscle Nerve. 2016;53(5):717-725.
  4. Shieh P, Sharma K, Kohrman B, Oh SJ. Amifampridine phosphate (FIRDAPSE®) is effective in a confirmatory phase 3 clinical trial in LEMS. J Clin Neuromuscul Dis. 2019;20(3):111-119.
  5. Harms L, Sieb J-P, Williams AE, et al. Long-term disease history, clinical symptoms, health status, and healthcare utilization in patients suffering from Lambert Eaton myasthenic syndrome: results of a patient interview survey in Germany. J Med Econ. 2012;15(3):521-530.
  6. Referenced with permission from the NCCN Clinical Practice Guidelines in Oncology (NCCN Guidelines®) Guideline for Small Cell Lung Cancer (Version v3.2023). © National Comprehensive Cancer Network, Inc. 2022. All rights reserved. Accessed February 20, 2023. To view the most recent and complete version of the guideline, go to NCCN.org. NCCN makes no warranties of any kind whatsoever regarding their content, use or application and disclaims any responsibility for their application or use in any way.
  7. Orange Book: Approved drug products with therapeutic equivalence evaluations. US Food and Drug Administration. 42nd ed. 2022:47,1260.
  8. Muppidi S, Wolfe GI, Barohn RJ. Diseases of the neuromuscular junction. In: Swaiman K, Ashwal S, Ferriero D, Schor N, eds. Pediatric Neurology: Principles and Practice. 5th ed. Philadelphia, PA: Elsevier; 2011:1549-1569.
  9. Senanayake N, Roman GC. Disorders of neuromuscular transmission due to natural environmental toxins. J Neurol Sci. 1992;107:1-13.
  10. National Organization for Rare Disorders (NORD) website. Rare disease database: Myasthenia gravis. Accessed December 9, 2022. https://rarediseases.org/rare-diseases/myasthenia-gravis/.
  11. Sanders DB. Lambert-Eaton myasthenic syndrome: diagnosis and treatment. Ann NY Acad Sci. 2003;998:500-508.
  12. Titulaer MJ, Lang B, Verschuuren JJ. Lambert-Eaton myasthenic syndrome: from clinical characteristics to therapeutic strategies. Lancet Neurol. 2011;10(12):1098-1107.
  13. Ghandhi L, Johnson BE. Paraneoplastic syndromes associated with small cell lung cancer. J Natl Compre Canc Netw. 2006;4(6):631-638.
  14. Titulaer MJ, Wirtz PW, Willems LNA, et al. Screening for small-cell lung cancer: a follow-up study of patients with Lambert-Eaton myasthenic syndrome. J Clin Oncol. 2008;26(26):4276-4281.
  15. Wirtz PW, Wintzen AR, Verschuuren JJ. Lambert-Eaton myasthenic syndrome has a more progressive course in patients with lung cancer. Muscle Nerve. 2005;32(2):226-229.
  16. Wirtz PW, Smallegange TM, Wintzen AR, Verschuuren JJ. Differences in clinical features between the Lambert-Eaton myasthenic syndrome with and without cancer: an analysis of 227 published cases. Clin Neurol Neurosurg. 2002;104(4):359-363.
  17. Tarr TB, Wipf P, Meriney SD. Synaptic pathophysiology and treatment of Lambert-Eaton myasthenic syndrome. Mol Neurolbiol. 2015;52(1):456-463.
  18. Meriney SD, Hulsizer SC, Lennon VA, Grinnell AD. Lambert-Eaton myasthenic syndrome immunoglobulins react with multiple types of calcium channels in small-cell lung carcinoma. Ann Neurol. 1996;40:739-749.
  19. Vincent A, Lang B, Newsom-Davis J. Autoimmunity to the voltage-gated calcium channel underlies the Lambert-Eaton myasthenic syndrome, a paraneoplastic disorder. TINS. 1989;12(12):496-502.
  20. Maddison P, Lang B, Mill K, Newsom-Davis J. Long term outcome in Lambert-Eaton myasthenic syndrome without lung cancer. J Neurol Neurosurg Psychiatry. 2001;70(2):212-217.
  21. Merino-Ramírez MÁ, Bolton CF. Review of the diagnostic challenges of Lambert-Eaton syndrome revealed through three case reports. Can J Neurol Sci. 2016;43(5):635-647.
  22. Gilhus NE. Lambert-Eaton myasthenic syndrome; pathogenesis, diagnosis, and therapy. Autoimmune Dis. 2011;2011:973808.
  23. Kesner VG, Shin JO, Dimachkie MM, Barohn RJ. Lambert-Eaton myasthenic syndrome. Neurol Clin. 2018;36(2):379-394.
  24. Lipka AF, Boldingh MI, van Zwet EW, et al. Long-term follow-up, quality of life, and survival of patients with Lambert-Eaton myasthenic syndrome. Neurology. 2020;94(5):e511-e520.
  25. Quartel A, Turbeville S, Lounsbury D. Current therapy for Lambert-Eaton myasthenic syndrome: development of 3,4-diaminopyridine phosphate salt as first-line symptomatic treatment. Curr Med Res Opin. 2010;26(6):1363-1375.
  26. Wirtz PW, Verschuuren JJ, van Dijk JG, et al. Efficacy of 3,4-diaminopyridine and pyridostigmine in the treatment of Lambert-Eaton myasthenic syndrome: a randomized, double-blind, placebo-controlled, crossover study. Clin Pharmacol Ther. 2009;86(1):44-48.
  27. Ivanovski T, Miralles F. Lambert-Eaton myasthenic syndrome: early diagnosis is key. Degener Neurol Neuromuscul Dis. 2019;9:27-37.
  28. Bain PG, Motomura M, Newsom-Davis J, et al. Effects of intravenous immunoglobulin on muscle weakness and calcium-channel autoantibodies in the Lambert-Eaton myasthenic syndrome. Neurology. 1996;47(3):678-683.
  29. Chalk CH, Murray NM, Newsom-Davis J, O'Neill JH, Spiro SG. Response of the Lambert-Eaton myasthenic syndrome to treatment of associated small-cell lung carcinoma. Neurology. 1990;40(10):1552-1556.
  30. Oh SJ, Sieb JP. Update on amifampridine as a drug of choice in Lambert-Eaton myasthenic syndrome. US J Neurol. 2014;10(2):83-89.
  31. Strupp M, Teufel J, Zwergal A, et al. Aminopyridines for the treatment of neurologic disorders. Neurol Clin Pract. 2017;7(1):65-76.
  32. Lindquist S, Stangel M. Update on treatment options for Lambert-Eaton myasthenic syndrome: focus on use of amifampridine. Neuropsychiatr Dis Treat. 2011;7:341-349.
  33. Data on file, Catalyst Pharmaceuticals.
  34. Kirsch GE, Narahashi T. 3,4-diaminopyridine. A potent new potassium channel blocker. Biophys J. 1978;22(3):507-512.
  35. Dodson PD, Forsythe ID. Presynaptic K+ channels: electrifying regulators of synaptic terminal excitability. TINS. 2004;27(4):210-217.
  36. Sudhof TC. Calcium control of neurotransmitter release. Cold Spring Harb Perspect Biol. 2012;4:a011353.
  37. Ojala KS, Ginebaugh SP, Wu M, et al. A high-infinity, partial antagonist effect of 3,4-diaminopyridine mediates action potential broadening and enhancement of transmitter release at NMJs. J Biol Chem. Published online January 17, 2021. doi: https://doi.org/10.1016/j.jbc.2021.100302.
  38. Kuo IY, Ehrlich BE. Signaling in muscle contraction. Cold Spring Harb Perspect Biol. 2015;47:a006023.
  39. Jacob S, Muppidi S, Guidon A, et al; International MG/COVID-19 Working Group. Guidance for the management of myasthenia gravis (MG) and Lambert-Eaton myasthenic syndrome (LEMS) during the COVID-19 pandemic. J Neurol Sci. 2020;412:116803.

Indication and Important Safety Information

indications and usage:

FIRDAPSE is a potassium channel blocker indicated for the treatment of Lambert-Eaton myasthenic syndrome (LEMS) in adults and pediatric patients 6 years of age and older.

CONTRAINDICATIONS

FIRDAPSE is contraindicated in patients with:

  • A history of seizures
  • Hypersensitivity to amifampridine phosphate or another aminopyridine

WARNINGS AND PRECAUTIONS

Seizures: FIRDAPSE can cause seizures. Consider discontinuation or dose-reduction of FIRDAPSE in patients who have a seizure while on treatment.

Hypersensitivity: If a hypersensitivity reaction such as anaphylaxis occurs, FIRDAPSE should be discontinued and appropriate therapy initiated.

ADVERSE REACTIONS

The most common (> 10%) adverse reactions are: paresthesia, upper respiratory tract infection, abdominal pain, nausea, diarrhea, headache, elevated liver enzymes, back pain, hypertension, and muscle spasms.

Please see full Prescribing Information for additional Important Safety Information.

To report SUSPECTED ADVERSE REACTIONS, contact Catalyst Pharmaceuticals at 1-844-347-3277 (1-844-FIRDAPSE) or FDA at 1-800-FDA-1088 or www.fda.gov/medwatch.

References:
  1. Yoon CH, Owusu-Guha J, Smith A, Buschur P. Amifampridine for the management of Lambert-Eaton myasthenic syndrome: a new take on an old drug. Ann Pharmacother. 2020;54(1):56-63.
  2. Full Prescribing Information for FIRDAPSE (amifampridine). Catalyst Pharma; 2022.
  3. Oh SJ, Scherbakova N, Kostera-Pruszczyk A, et al; LEMS Study Group. Amifampridine phosphate (FIRDAPSE®) is effective and safe in a phase 3 clinical trial in LEMS. Muscle Nerve. 2016;53(5):717-725.
  4. Shieh P, Sharma K, Kohrman B, Oh SJ. Amifampridine phosphate (FIRDAPSE®) is effective in a confirmatory phase 3 clinical trial in LEMS. J Clin Neuromuscul Dis. 2019;20(3):111-119.
  5. Harms L, Sieb J-P, Williams AE, et al. Long-term disease history, clinical symptoms, health status, and healthcare utilization in patients suffering from Lambert Eaton myasthenic syndrome: results of a patient interview survey in Germany. J Med Econ. 2012;15(3):521-530.
  6. Referenced with permission from the NCCN Clinical Practice Guidelines in Oncology (NCCN Guidelines®) Guideline for Small Cell Lung Cancer (Version v3.2023). © National Comprehensive Cancer Network, Inc. 2022. All rights reserved. Accessed February 20, 2023. To view the most recent and complete version of the guideline, go to NCCN.org. NCCN makes no warranties of any kind whatsoever regarding their content, use or application and disclaims any responsibility for their application or use in any way.
  7. Orange Book: Approved drug products with therapeutic equivalence evaluations. US Food and Drug Administration. 42nd ed. 2022:47,1260.
  8. Muppidi S, Wolfe GI, Barohn RJ. Diseases of the neuromuscular junction. In: Swaiman K, Ashwal S, Ferriero D, Schor N, eds. Pediatric Neurology: Principles and Practice. 5th ed. Philadelphia, PA: Elsevier; 2011:1549-1569.
  9. Senanayake N, Roman GC. Disorders of neuromuscular transmission due to natural environmental toxins. J Neurol Sci. 1992;107:1-13.
  10. National Organization for Rare Disorders (NORD) website. Rare disease database: Myasthenia gravis. Accessed December 9, 2022. https://rarediseases.org/rare-diseases/myasthenia-gravis/.
  11. Sanders DB. Lambert-Eaton myasthenic syndrome: diagnosis and treatment. Ann NY Acad Sci. 2003;998:500-508.
  12. Titulaer MJ, Lang B, Verschuuren JJ. Lambert-Eaton myasthenic syndrome: from clinical characteristics to therapeutic strategies. Lancet Neurol. 2011;10(12):1098-1107.
  13. Ghandhi L, Johnson BE. Paraneoplastic syndromes associated with small cell lung cancer. J Natl Compre Canc Netw. 2006;4(6):631-638.
  14. Titulaer MJ, Wirtz PW, Willems LNA, et al. Screening for small-cell lung cancer: a follow-up study of patients with Lambert-Eaton myasthenic syndrome. J Clin Oncol. 2008;26(26):4276-4281.
  15. Wirtz PW, Wintzen AR, Verschuuren JJ. Lambert-Eaton myasthenic syndrome has a more progressive course in patients with lung cancer. Muscle Nerve. 2005;32(2):226-229.
  16. Wirtz PW, Smallegange TM, Wintzen AR, Verschuuren JJ. Differences in clinical features between the Lambert-Eaton myasthenic syndrome with and without cancer: an analysis of 227 published cases. Clin Neurol Neurosurg. 2002;104(4):359-363.
  17. Tarr TB, Wipf P, Meriney SD. Synaptic pathophysiology and treatment of Lambert-Eaton myasthenic syndrome. Mol Neurolbiol. 2015;52(1):456-463.
  18. Meriney SD, Hulsizer SC, Lennon VA, Grinnell AD. Lambert-Eaton myasthenic syndrome immunoglobulins react with multiple types of calcium channels in small-cell lung carcinoma. Ann Neurol. 1996;40:739-749.
  19. Vincent A, Lang B, Newsom-Davis J. Autoimmunity to the voltage-gated calcium channel underlies the Lambert-Eaton myasthenic syndrome, a paraneoplastic disorder. TINS. 1989;12(12):496-502.
  20. Maddison P, Lang B, Mill K, Newsom-Davis J. Long term outcome in Lambert-Eaton myasthenic syndrome without lung cancer. J Neurol Neurosurg Psychiatry. 2001;70(2):212-217.
  21. Merino-Ramírez MÁ, Bolton CF. Review of the diagnostic challenges of Lambert-Eaton syndrome revealed through three case reports. Can J Neurol Sci. 2016;43(5):635-647.
  22. Gilhus NE. Lambert-Eaton myasthenic syndrome; pathogenesis, diagnosis, and therapy. Autoimmune Dis. 2011;2011:973808.
  23. Kesner VG, Shin JO, Dimachkie MM, Barohn RJ. Lambert-Eaton myasthenic syndrome. Neurol Clin. 2018;36(2):379-394.
  24. Lipka AF, Boldingh MI, van Zwet EW, et al. Long-term follow-up, quality of life, and survival of patients with Lambert-Eaton myasthenic syndrome. Neurology. 2020;94(5):e511-e520.
  25. Quartel A, Turbeville S, Lounsbury D. Current therapy for Lambert-Eaton myasthenic syndrome: development of 3,4-diaminopyridine phosphate salt as first-line symptomatic treatment. Curr Med Res Opin. 2010;26(6):1363-1375.
  26. Wirtz PW, Verschuuren JJ, van Dijk JG, et al. Efficacy of 3,4-diaminopyridine and pyridostigmine in the treatment of Lambert-Eaton myasthenic syndrome: a randomized, double-blind, placebo-controlled, crossover study. Clin Pharmacol Ther. 2009;86(1):44-48.
  27. Ivanovski T, Miralles F. Lambert-Eaton myasthenic syndrome: early diagnosis is key. Degener Neurol Neuromuscul Dis. 2019;9:27-37.
  28. Bain PG, Motomura M, Newsom-Davis J, et al. Effects of intravenous immunoglobulin on muscle weakness and calcium-channel autoantibodies in the Lambert-Eaton myasthenic syndrome. Neurology. 1996;47(3):678-683.
  29. Chalk CH, Murray NM, Newsom-Davis J, O'Neill JH, Spiro SG. Response of the Lambert-Eaton myasthenic syndrome to treatment of associated small-cell lung carcinoma. Neurology. 1990;40(10):1552-1556.
  30. Oh SJ, Sieb JP. Update on amifampridine as a drug of choice in Lambert-Eaton myasthenic syndrome. US J Neurol. 2014;10(2):83-89.
  31. Strupp M, Teufel J, Zwergal A, et al. Aminopyridines for the treatment of neurologic disorders. Neurol Clin Pract. 2017;7(1):65-76.
  32. Lindquist S, Stangel M. Update on treatment options for Lambert-Eaton myasthenic syndrome: focus on use of amifampridine. Neuropsychiatr Dis Treat. 2011;7:341-349.
  33. Data on file, Catalyst Pharmaceuticals.
  34. Kirsch GE, Narahashi T. 3,4-diaminopyridine. A potent new potassium channel blocker. Biophys J. 1978;22(3):507-512.
  35. Dodson PD, Forsythe ID. Presynaptic K+ channels: electrifying regulators of synaptic terminal excitability. TINS. 2004;27(4):210-217.
  36. Sudhof TC. Calcium control of neurotransmitter release. Cold Spring Harb Perspect Biol. 2012;4:a011353.
  37. Ojala KS, Ginebaugh SP, Wu M, et al. A high-infinity, partial antagonist effect of 3,4-diaminopyridine mediates action potential broadening and enhancement of transmitter release at NMJs. J Biol Chem. Published online January 17, 2021. doi: https://doi.org/10.1016/j.jbc.2021.100302.
  38. Kuo IY, Ehrlich BE. Signaling in muscle contraction. Cold Spring Harb Perspect Biol. 2015;47:a006023.
  39. Jacob S, Muppidi S, Guidon A, et al; International MG/COVID-19 Working Group. Guidance for the management of myasthenia gravis (MG) and Lambert-Eaton myasthenic syndrome (LEMS) during the COVID-19 pandemic. J Neurol Sci. 2020;412:116803.
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